Airfoil having porous metal filled cavities

ABSTRACT

A turbine airfoil used in a gas turbine engine includes a plurality of cavities opening in a direction facing the airfoil surface, each cavity having cooling holes communicating with an internal cooling fluid passage of the airfoil, and the airfoil surface above the cavity being a thermal barrier coating and having a plurality of cooling holes communicating with the cavity, where each cavity is filled with a porous metal or foam metal material. Heat is transferred from the airfoil surface to the porous metal, and a cooling fluid passing through the porous metal attracts heat from the porous metal and flows out the holes and onto the airfoil surface to cool the airfoil.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit to an earlier co-pending Provisional Application Ser. No. 60/677,900 filed on May 5, 2005 and entitled Airfoil Having Porous Metal Filled Cavities.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an airfoil for use in a gas turbine engine, either as a blade or a vane, in which the airfoil includes a plurality of porous metal filled cavities with a thermal barrier coating applied over the porous metal, the porous metal allowing cooling air to flow through it onto the TBC producing a cooling air film to cool the airfoil.

2. Description of the Related Art including information disclosed under 37 CFR 1.97 and 1.98

Prior art airfoils use a variety of ways to cool the airfoil using cooling air passing through and over the surface of the airfoil. U.S. Pat. No. 4,629,397 issued to Schweitzer on Dec. 16, 1986 shows an airfoil (FIG. 4) having a plurality of unobstructed cooling ducts 3 and lands 5 enclosed by an inner layer of metal felt 4 and an outer layer of heat insulating ceramic material 6 which partially penetrates into the metal felt 4 to form a bonding zone between the felt 4 and the ceramic material 6. Thus, any heat passing through the ceramic layer 6 is introduced into the large surface area of the metal felt 4 enabling the latter to efficiently introduce the heat into a cooling medium flowing in the ducts 3, thereby preventing thermal loads from adversely affecting the metal core to any appreciable extent.

BRIEF SUMMARY OF THE INVENTION

The present invention provides an airfoil used in a gas turbine engine which includes a plurality of open ducts or cavities, these cavities being filled with a porous metal material to allow cooling air to pass through the porous metal, and a thermal barrier coating (TBC) applied on top of the porous metal, the TBC having cooling air holes to allow for the cooling air passing through the porous metal to flow onto the outer surface of the TBC to cool the airfoil. Cooling holes are located in the base of the cavities and through the TBC to allow cooling fluid to flow from within the airfoil to the external surface of the TBC. The porous metal acts as a support for the TBC, and also provides improved heat transfer from the airfoil to the cooling air passing through the porous metal since the porous metal better dissipates the heat throughout itself. The porous metal also acts to spread out the flow of cooling air as the cooling air passes through the porous metal, thereby increasing the heat transfer effect.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

FIG. 1 shows a turbine airfoil having a pressure side with a plurality of square-shaped porous metal filled cavities.

FIG. 2 shows a cross-sectional view of a surface of the airfoil with the cavity filled with a porous metal and a TBC applied over the porous metal.

FIG. 3 shows one of the square-shaped cavities with a porous metal filling the cavity and a plurality of cooling holes in the base of the cavity and in the TBC applied over the porous metal.

FIG. 4 shows a Prior Art airfoil with a porous metal and a Ceramic TBC layer from U.S. Pat. No. 4,629,397.

DETAILED DESCRIPTION OF THE INVENTION

A gas turbine engine includes airfoils within the direct the flow of gas passing through it and to remove power from flowing gas. The airfoil can be either a rotary blade or a guide vane. An airfoil 10 of the blade type is shown in FIG. 1 and includes a plurality of cavities 12 or ducts opening onto a surface of the airfoil. These cavities are formed by ribs 17 crossing each other that also act as rigid supports for the airfoil. The cavities in the present invention are shown as rectangular in shape having equal length and width. However, any shape and size could be used under the principal of the present invention.

FIG. 2 shows a cross-sectional view of the airfoil wall 14 having the cavities formed by the ribs 17. Each cavity is filled with a porous metal 24. The porous metal is sometimes referred to as a foam metal or a fiber metal. The base 15 of the cavity includes a plurality of cooling holes 18 to pass cooling air from a central passageway inside the airfoil 10 into the porous metal filled cavity 12. A thermal barrier coating (TBC) 16 is applied over the porous metal to form an outer surface of the airfoil. The porous metal 24 acts as an insulating layer and acts to support the TBC and well as provide increased heat transfer from the airfoil to the cooling air. The TBC also has a plurality of cooling holes 20 to allow for the cooling air to pass onto the outer surface of the airfoil 10. In this embodiment, the porous metal is of a low density with respect to other porous metals in order to allow cooling air to flow through the material for heat transfer purposes.

The cooling holes 18 in the base 15 of the cavity is located on an opposite side of the cavity 12 than the cooling holes 20 in the TBC in order to force the cooling air passing through the porous metal 24 to pass through as much of the porous metal 24 as possible, thereby increasing the heat transfer effect of the porous metal 24 to the cooling air.

FIG. 3 shows a single cavity of the present invention in which the base 15 of the cavity includes a plurality of cooling holes 18 arranged along one side of the cavity 12. The cavity 12 is filled with the porous metal 24, and the TBC 16 is applied over the porous metal 24. Cooling holes 20 in the TBC are placed on an opposite side of the cavity 12 from the cooling holes 18 in the base 15 in order to force the cooling air to pass through as much of the porous metal as possible.

The porous metal used in the present invention can be any of the well-known porous metals used in gas turbine engines. The preferred material would be one that has a high melting point, and a high conductivity to magnify the effective cooling passage heat transfer coefficient at high temperatures found in the gas turbine art.

The size and shape of the cavities can be varied to provide any desired heat transfer effect. Cavity shapes can be square as shown in the Figures, rectangular, triangular, or even oval. The depth to width ratio of the cavity would depend upon the strength required for the side walls to support. TBCs having high strengths can be supported by larger cavities. The packing density of the porous metal can be regulated or varied within the airfoil to effect heat transfer rates. Even the relative density of the porous metal within a cavity can be varied to affect the heat transfer rate. Providing a higher density of porous metal at the interface of the TBC will improve the strength of the porous metal to secure the TBC. 

1. A turbine airfoil having an outer airfoil surface, comprising: A cavity opening toward the airfoil surface; A cooling hole in a base of the cavity for supplying a cooling fluid into the cavity; A porous material substantially filling the cavity; The outer airfoil surface being secured over the cavity; and, A cooling hole in the outer airfoil surface and communicating with the cavity such that a cooling fluid passing through the cooling hole in the base will pass through the porous metal and then through the cooling hole in the airfoil surface.
 2. The turbine airfoil of claim 1, and further comprising: The base includes a plurality of cooling holes, and the airfoil surface includes a plurality of cooling holes.
 3. The turbine airfoil of claim 1, and further comprising: The cooling hole in the base is located near one side of the cavity, and the cooling hole in the airfoil is located near an opposite side of the cavity.
 4. The turbine airfoil of claim 2, and further comprising: The cooling holes in the base are located near one side of the cavity, and the cooling holes in the airfoil are located near an opposite side of the cavity.
 5. The turbine airfoil of claim 1, and further comprising: The porous metal is of a low density such that heat is transferred from the airfoil surface into the porous metal, and then from the porous metal into cooling air flowing through the porous metal.
 6. The turbine airfoil of claim 1, and further comprising: The cavity is substantially rectangular in shape.
 7. The turbine airfoil of claim 1, and further comprising: The airfoil includes a plurality of the cavities.
 8. The turbine airfoil of claim 1, and further comprising: The outer airfoil surface is a thermal barrier coating.
 9. A process for cooling a turbine airfoil used in a gas turbine engine, the process comprising the steps of: Providing for an airfoil surface with a cooling hole therein; Providing for a cavity opening toward the airfoil surface; Filling the cavity with a porous metal; Providing for a cooling hole in a base of the cavity; and, Passing a cooling fluid through the cooling hole in the base, then through the porous metal, and then through the hole in the airfoil surface to cool the airfoil.
 10. The process of claim 9, and further comprising the step of: Providing for the airfoil surface to form a closed spaced with the cavity.
 11. The process of claim 9, and further comprising the steps of: Providing for the hole in the base to be located near one side of the cavity; and, providing for the hole in the airfoil surface to be near an opposite side of the cavity.
 12. The process of claim 9, and further comprising the step of: Providing for a plurality of holes in the base; and, Providing for a plurality of holes in the airfoil surface.
 13. The process of claim 9, and further comprising the step of: Providing for a plurality of cavities each with a base cooling hole and an airfoil surface cooling hole, and each filled with a porous metal.
 14. The process of claim 9, and further comprising the step of: Providing for the airfoil surface to be thermal barrier coating.
 15. A turbine airfoil, comprising: A cavity having a base, the cavity opening in a direction toward an outer surface of the airfoil; A cooling hole in the base; A porous metal means located within the cavity to draw heat from the airfoil surface and pass the heat to a cooling fluid passing through the cavity; and, An outer airfoil surface over the porous metal means.
 16. The turbine airfoil of claim 15, and further comprising: A cooling hole in the outer airfoil surface in fluid communication with the cavity.
 17. The turbine airfoil of claim 15, and further comprising: The outer airfoil surface forming a closed cavity.
 18. The turbine airfoil of claim 16, and further comprising: The cooling hole in the base being located near one side of the cavity, and the cooling hole in the outer airfoil surface being located near an opposite side of the cavity.
 19. The turbine airfoil of claim 15, and further comprising: The outer airfoil surface being a thermal barrier coating.
 20. The turbine airfoil of claim 16, and further comprising: A plurality of cavities, each cavity including a plurality of cooling holes in the base and a plurality of cooling holes in the outer airfoil surface associated with the respective cavity, the cooling holes in the base being located near one side of the cavity while the cooling holes in the outer airfoil surface being located near an opposite side of the cavity. 